This study investigated the effect of temperature on the aspect-ratio etching of SiO<sub>2</sub> in CF<sub>4</sub>/H<sub>2</sub>/Ar plasma using patterned samples of a 200 nm trench in a low-temperature reactive-ion etching system. Lower temperatures resulted in higher etch rates and aspect ratios for SiO<sub>2</sub>. However, the plasma property was constant with the chuck temperature, indicated by the line intensity ratio from optical emission spectroscopy monitoring of the plasma. The variables obtained from the characterization of the etched profile for the 200 nm trench after etching were analyzed as a function of temperature. A reduction in the necking ratio affected the etch rate and aspect ratio of SiO<sub>2</sub>. The etching mechanism of the aspect ratio etching of SiO<sub>2</sub> was discussed based on the results of the surface composition at necking via energy-dispersive X-ray spectroscopy with temperature. The results suggested that the neutral species reaching the etch front of SiO<sub>2</sub> had a low sticking coefficient. The bowing ratio decreased with lowering temperature, indicating the presence of directional ions during etching. Therefore, a lower temperature for the aspect ratio etching of SiO<sub>2</sub> could achieve a faster etch rate and a higher aspect ratio of SiO<sub>2</sub> via the reduction of necking than higher temperatures.